William Jeffery, Professor of Biology
University of Maryland, College Park, MD

Presentation Title: Cavefish: Evolution in the Dark

Cave animals have adapted to the challenges of life in perpetual darkness by losing their eyes and pigmentation and enhancing other sensory systems, such as taste, smell, and tactile senses. Although the sensory gains are easily explained by natural selection, the losses are more difficult to explain because they seem to have no immediate benefits. Recent studies in the Mexican cavefish (Astyanax mexicanus) show that eye degeneration is developmentally linked to adaptive gains in the gustatory system via evolutionary changes in a pleiotropic gene called "sonic hedgehog." Thus, cavefish may illustrate a general phenomenon in biology in which pleiotropy and indirect selection guide the course and extent of evolution. Another benefit for cavefish living in dark caves is the absence of predators, which promotes survival by evolving an unusual suite of feeding behaviors. These behaviors would be risky in more complex, well-lit environments, such as exist on the Earth’s surface, illustrating the importance of environmental complexity as a driving force in evolution.

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Research Interests

I am interested in the evolution of development. Several different animals are used in my research. The teleost Astyanax mexicanus is a single species with eyed surface dwelling and blind cave dwelling forms. I want to understand the developmental and evolutionary mechanisms responsible for phenotypic changes in Astyanax cavefish. I am also interested in the ancestry of the neural crest in chordates. For this research I use sea squirts (ascidians), especially Ciona intestinalis, which has a completely sequenced genome.

Recent Publications

Jeffery, W.R. 2001. Cavefish as a Model System in Evolutionary Developmental Biology.  Developmental Biology 231(1):1-12.

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Yamamoto, Y, Jeffery, W.R. 2000. Central role for the lens in cave fish eye degeneration. Science 289: 631-633.

Jeffery, W.R. 2005. Adaptive evolution of eye degeneration in the Mexican Blind Cavefish. Journal of Heredity 96(3):185-196. doi:10.1093/jhered/esi028

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Jeffery, W.R., Strickler, A.G, and Yamamoto, Y. 2003. To See or Not to See: Evolution of Eye Degeneration in Mexican Blind Cavefish. Integrative and Comparative Biology. 43(4):531-541. doi:10.1093/icb/43.4.531

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Jeffery, W.R. 2008. Emerging model systems in evo-devo: cavefish and microevolution of development. Evolution&Development 10(3):265-272

Resources for Teaching

Photographic diary of a field expedition

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Power point slide show from the field expedition

Launch Power Point Presentation

"Morph" movies demonstrating the morphological changes between surface and cavefish made by Tom Hooven.

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Espinasa, M. and Espinasa, L. 2008. Losing Sight of Regressive Evolution. Evolution: Education and Outreach. Vol 1(4):509-516. DOI: 10.1007/s12052-008-0094-z

This article presents the authors’ approach to teaching about the evolution of blind cave fish.

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From Understanding Evolution: